Amplitude shift keying (ASK) is a signaling method where the message is encoded in the amplitude of the transmitted waveform. A typical ASK receiver includes a receiving antenna followed by an analog front-end (AFE) which down-converts the wireless signal from the receiving antenna by extracting the signal envelope. The signal envelope is quantized into discrete values using an analog-to-digital converter (ADC) for further digital signal processing (DSP) since the received signal suffers from various non-idealities.
Examples of non-idealities include the following:                i) Phase jitter during modulation at the transmitter (a bounded time-offset uncertainty on the symbol transition time grid), which causes a time-varying deviation of the transmitted symbol period, manifesting as shifted rising and falling edges of symbols of a signal from their nominal positions.        ii) Bandwidth limited wireless channel introduces inter-symbol interference (ISI) into the received signal. ISI increases with the transmission data rate, when the data rate exceeds the available channel bandwidth.        iii) Channels and the AFE can induce time-varying gain for each signal constellation point, which makes symbol detection difficult at the receiver.        iv) A high-pass filter effect arising from ac coupling and/or a power regulator in the AFE at the receiver, which suppresses low-frequency components to cause baseline wander in the received signal.        
These signal distortions necessitate DSP at the receiver to reliably recover the transmitted message without incurring symbol errors.
Traditionally, transversal, lattice, or block adaptive equalizers have been used to compensate for ISI and time-varying signal gain. However, in burst communications and in constrained frame formats with few or no training symbols, the equalizers may not be adequately trained. Consequently, the use of an equalizer with non-converged filter weights will yield a large residual ISI. Blind equalizers are an attractive alternative but their convergence time is generally long (in the order of several thousand symbols), making them unsuitable for burst communications.
Phase jitter can be combated using fractionally-spaced equalization. Unfortunately, for the same reasons described above, a poorly converged equalizer is of little use in compensating phase jitter in burst communications.
In the literature, use of decision feedback equalizers and of low-pass filtered symbol decisions to restore the low-frequency components in the ADC's digitized signal output has been suggested to overcome baseline wander. However, these methods have increased computational complexity making them unsuitable for hardware implementation. Moreover, the equalizer based method would need increased filter length and training period, whereas difficult manual tuning of parameters is required in designing the low-pass filter used to restore the low-frequency components.